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FIREBALLS

By Jeremy Tatum and Damien Lemay

Exceptionally bright meteors that are spectacular enough to attract the
attention of the public and light up the countryside over a wide area are
generally referred to as fireballs. With camera networks and satellite-based
detections now providing statistical information on the entry of fireballs into
Earth's atmosphere, the main reasons to collect fireball reports are to assist
with meteorite recovery and to provide orbital information for recovered
meteorites. Rapid recovery of meteorites is vital for the study of short-lived
radioactive isotopes produced by cosmic ray bombardment of the meteorite while
in interplanetary space. Small but potentially recoverable meteorites can be
produced by fireballs that are no brighter than magnitude -6. A very slow
fireball with no indication of terminal breakup is a good candidate for
meteorite survival. The presence of delayed sound indicates penetration into the
lower atmosphere and probable meteorite fall. The value of a meteorite is
significantly greater when we know something of its atmospheric trajectory and
orbit. Visual data can, under favourable circumstances, be used to obtain an
approximate atmospheric trajectory. The Meteorites and Impacts Advisory
Committee, MIAC (Comité consultatif sur les météorites et les impacts, CCMI),
of the Canadian Space Agency maintains a website with images and information on
fireballs, meteorites, and impact craters at miac.uqac.uquebec.ca/.
If you want information on recent Canadian fireball or meteorite events, check
the MIAC/CCMI bulletin board at:

If you do not have access to the web, write a brief report with the following
information:

(1) The name, telephone number, and
address of the observer(s).

(2) The time of occurrence (and
uncertainty in this time).

(3) The location of the observer at
the time the fireball was seen (preferably in precise longitude and
latitude).

(4) The beginning and ending points
of the fireball, in terms of either right ascension and declination or azimuth
and elevation. If possible, indicate the uncertainty in these angles. Indicate
whether the true beginning was observed and whether the ending point was blocked
by horizon objects.

(5) A direct apparent magnitude
estimate if possible; if not, note whether the fireball was brighter than,
approximately equal to, or fainter than the full Moon.

(6) The duration of the fireball and
the persistent train (if any).

(7) A qualitative description of the
event (colour, flares, fragmentation, and sound). Report the absence as well as
the presence of features such as sound and fragmentation. In the case of sound,
report the delay between the fireball appearance and the sound.